Couldn’t you just take a (spacecraft3.dll) object and disassociate it from its mesh and rename or just make the mesh very small.
Then make the object weight 1 million tons or so
Next, using the (universal cargo deck) attach it to the base of your spacecraft, or the side that is on the ground if you want it to be horizontal.
This should keep most craft stationary at full thrust, I believe.
Unfortunately I won’t be able to try it out until this weekend.